Patent GB-1381147-A (GB)
Title: Method of and apparatus for friction welding
IPC: B23K20/12
Filed: 1972-05-16
Abstract: 1381147 Welding by pressure CLARKE CHAPMAN Ltd 4 April 1973 [16 May 1972] 22934/72 Heading B3R In friction welding first and second outer workpieces to an intermediate workpiece the completion of predetermined minimum amounts of burn-off is determined by initiating, in response to the contacting of the intermediate. workpiece by both outer workpieces, two relative movements, one being between a first operator member and first mechanism which is operable in response to a predetermined amount of said one relative movement, the other being between a second operator member and second mechanism which is operable in response to a predetermined amount of said other relative movement, the relative movements being indicative, respectively, of the burn-off produced by rubbing between the first and intermediate workpieces and between the second and intermediate workpieces and by deriving from the operation of the mechanisms indication of completion of the predetermined amounts of burn-off. In an embodiment a double-ended friction welding machine comprises opposed heads 10, 12 which may be advanced towards one another by hydraulic rams and which carry power driven chucks for holding the two outer workpieces. The intermediate workpiece is held non- rotatably but free for axial movement between the heads 10, 12. On the head 10 a microswitch 14 is mounted having an operating plunger carrying a roller 18 and slidable in a bracket on the head is a spindle 26 having a cam face 42 for engaging the roller 18. A spring 46 is arranged between the spindle and the bracket. A similar microswitch 16, spindle 28 and spring 48 are provided on the head 12. The heads 10, 12 are slidable on a base 49, Fig. 2, on which is mounted a clamp mechanism comprising a body 50 supporting an hydraulic piston and cylinder 52 operable to move a clamp plate 54 towards or away from the body 50. Two rods 56, 58 are slidable in the body 50 against springs 60, 62 and can be clamped by the plate 54. An end 38 on spindle 26 engages a striker head 64 on the rod 56 and an end 40 on the spindle 28 engages a striker head 66 on the rod 58. In operation workpieces are secured in the heads 10, 12 and an intermediate workpiece is positioned between them. The heads 10, 12 are moved together while their workpieces are rotated and the spindle end 38 will push the rod 56 to the right, the spring 26 being stronger than the spring 60 and the spindle end 40 will push the rod 58 to the left. When the outer workpieces both abut the intermediate workpiece a rise in the pressure of the hydraulic system operating the rams causes the piston and cylinder device 52 to clamp the rods 56, 58 against the body 50. Further movement together of the heads causes burn off and movement of the heads relatively to the spindles 26, 28 occurs for a predetermined distance until the plungers of the microswitches are operated by the cam faces 42, 44 to light pilot lights. The ram pressure is then increased and rotation of the outer workpiece is stopped. After welding the parts return to their initial positions, micro switches possibly monitoring the return of the spindles 26, 28 and rods 56, 58 to their start positions. In a modification a timer could be started when all three workpieces abut so that if a predetermined time has not elapsed before the minimum burn-off movements have been indicated the welds are rejected as faulty.